FADEC, BAG 5

Question 1

What is the FADEC’s intended design?

Answer 1

The FADEC is designed to deliver optimal engine performance based on pilot input while preserving engine life through the constant monitoring of defined operating limits.

Question 2

Which incorporated unit is designed to match the engines N1’s?

Answer 2

The FADEC system incorporates a dual-channel (A and B) computer Digital Engine Control Unit (DECU) that controls engine operation and is designed to match the N1 of both engines.

Question 3

Are you doomed if there is a major FADEC failure??

think, emergency back-up

Answer 3

If neither channel can control the engine, a major FADEC failure has occurred and fuel metering is frozen. Backup operation is available through a secondary device known as the Emergency
Backup Control Auxiliary Unit (EBCAU).

Question 4

What is the FADEC made up of?

Answer 4

The FADEC system is made up of airframe, electrical, and hydro-mechanical components.

Question 5

What are the FADEC airframe components?

Answer 5

Airframe components consist of switches, buttons, indicators, warning lights, and DECU power supply.

Question 6

What are the FADEC electrical components made of?

Answer 6

Electrical components consist of control sensors, indicator sensors, DECU dual-channel alternators, a resolver (fuel meter), stepper motor, stop electrovalve, start electrovalve, ignition unit, starter, and the EBCAU.

Question 7

What are the FADEC mechanical components made of?

Answer 7

Engine components consist of check valves, start injectors, high and low-pressure fuel pumps, filters, the main injection system, and fuel metering unit.

Question 8

Which indications are result of a fault in the FADEC system, with FCS in the OFF position?

Answer 8

A flashing GOV light or FADEC FAIL light on the WCA panel indicates a fault in the system and should be investigated prior to starting.

Question 9

FCS in OFF, what does a steady GOV indicate?

Answer 9

A steady GOV light allows for a one-time recycling of the battery relay switches to extinguish the light prior to start.

Question 10

FCS in OFF, what happens when battery power is applied?

Answer 10

FADEC performs a self test, will also provide the cockpit of any indication of a failure, GOV or FADEC FAIL on the WCA

Question 11

What initiates the START sequence?

Answer 11

When the FCS is moved to the IDLE or FLIGHT position with the rotor brake off, the START sequence is initiated.

Question 12

What action will inhibit the START sequence?

Answer 12

In the event the FCS is placed in the IDLE or FLIGHT position prior to the battery being turned
on, FADEC logic will prevent the START sequence from occurring.

Question 13

When is the START sequence “self-sustaining”?

Answer 13

The start becomes self-sustaining at 45% N1 with a normal idle speed of 68% N1.

Question 14

Why would the FADEC AUTOMATICALLY secure a START sequence?

Answer 14

Automatic engine shutdown will occur when the FADEC detects a TOT of 840 °C or if the TOT does not exceed 100 °C by 27% N1.

Question 15

What does the N1% have to be below in order to allow an engine restart?

Answer 15

In the event of an inflight restart, the start sequence will not initiate until N1 is below 17 percent.

Question 16

What does placing the FCS in IDLE do?

Answer 16

If the FCS is placed in the IDLE position, the engine will complete the start sequence and remain at 68% N1
until advanced to the FLIGHT position.

Question 17

When does the DECU’s power source become an alternator?

Answer 17

Once N1 reaches 65 percent, the DECUs power source becomes its respective dual-channel alternator.
If the dual channel alternators fail, power to the DECU will be provided by the aircraft battery.

Question 18

What does the FADEC do when FCS is placed in FLIGHT position?

Answer 18

Once the FCS is advanced to the FLIGHT position, the FADEC will operate on FLIGHT governing laws. Once the FADEC is established in the FLIGHT phase it monitors for single and dual engine operation.

Question 19

What is/are the FADEC’S Anticipator and Load Sharing Operations? How does it work?

Answer 19

The N1 is adjusted to maintain a constant N2 and NR speed. During flight, collective lever position represents the power required and will determine the N1 operating datum. This function, also known as anticipation, permits an initial adaptation of the N1 or gas generator to balance the power required to keep N2 constant.

Question 20

Which FADEC system reduces the reaction time of the engines by producing an instant signal load of variation?

Answer 20

The anticipator also supplies an instant signal of load variation to the FADEC which reduces the reaction
time of the engines.

Question 21

What is the FADEC’s ‘Load sharing’ purpose? How does the load sharing operate?

Answer 21

To ensure alignment of the engines, an additional function of the FADEC, known as load-sharing, matches
the N1 of the engines by increasing the output of the lower engine until engine outputs are matched.

Question 22

How is NR (rotor speed) ultimately determined?

Answer 22

N2 controller, which determines NR speed, is referenced to balance the power required versus the power supplied. Thus, the N1 datum is derived from anticipator position, the N2 controller and the load-sharing function. The N1 datum is then restricted in order to assure optimal acceleration, deceleration, torque limiting, and adherence to OEI ratings. This N1 datum determines the appropriate fuel flow to maintain a constant N2 without droop.

Question 23

What does the Fuel Flow Limiter prevent?

Answer 23

The fuel flow limiter is referenced to prevent surge or flameout.

Question 24

When does the FADEC stop torque?

Answer 24

the FADEC stops torque at 110 percent (11.0)

Question 25

How many safety features of the FADEC will add power during NR mismanagement?

Answer 25

two built-in FADEC safety features

Question 26

What does the first built in safety feature do?

Answer 26

will cause the FADEC to begin increasing Torque (TRQ) up to 118 percent (11.8) when NR decreases
to <335 RPM.

Question 27

What happens if the rotor speed continues to decline?

Answer 27

If NR continues to decrease to less than 317 RPM, the torque stop will increase up to a minimum of 125
percent (12.5). This feature also senses the rate at which NR droop is occurring.

Question 28

What happens if rotor is drooping @ 2rpm/sec?

Answer 28

the torque stop will immediately be increased to a minimum of 125 percent (12.5) as soon
as NR droop reaches 324 RPM.

Question 29

The second FADEC safety feature will allow N1 to increase past the 2-min OEI rating when N1 is the FLI
limiting factor under the following conditions. State those two conditions.

Answer 29

If NR <324 RPM and is decaying at 17.5 RPM a second or greater, the N1 will increase by +0.28
percent past the N1, 2-min OEI rating.

Anytime NR <317 RPM N1 will increase by +0.28 percent.

Question 30

What is a level 1 failure?

Answer 30

(loss of redundancy)
should be evident on the Systems Status page with an FCS in the FLIGHT position. Such failures will be annotated by a flashing GOV light on the WCA panel when the FADEC control switch is in the IDLE or OFF position.

Question 31

What is a level 2 failure?

Answer 31

(loss of a nonredundant resource),
such as FADEC crosstalk failure, will manifest as a steady GOV light on the WCA panel at the time of failure. Level 2 failures represent a degraded operating state of the FADEC.

Question 32

What is a level 3, major FADEC, failure?

Answer 32

manifests a FADEC FAIL annunciation on the WCA panel along with illumination of the red engine status light. Level 3 failures (major FADEC failure), such as a dual-channel FADEC failure, represent a total failure of the respective FADEC. Fuel flow on the affected engine will be frozen at its present value.

Question 33

What should aircrew not use under a level 1 failure?

Answer 33

Training mode, simulating engine failure.